thermal: db8500: Depromote debug print

We are not interested in getting this debug print on our
console all the time.

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Stephan Gerhold <stephan@gerhold.net>
Fixes: 6c375ecc ("thermal: db8500: Rewrite to be a pure OF sensor")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20191119074650.2664-1-linus.walleij@linaro.org